Hyperbaric Oxygen Therapy

 

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Hospital  Affiliation

Hoag Memorial Hospital, Newport Beach, CA

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What are the physiological mechanisms of action caused by HBO2?

HyperOxygenation: HBO2 physically dissolves extra oxygen into the blood plasma. The delivery is to the tissues. Breathing pure oxygen at two to three times normal pressure delivers 10-15 times as much physically dissolved oxygen to tissues. This can increase the tissue oxygen in compromised tissues to greater-than-normal values. HyperOxygenation has been demonstrated to induce formation of new capillaries in ischemic or poorly perfused wounds. Therefore, it is useful in the treatment of ischemic based compromised wounds, flaps, and grafts. It is also helpful in some infections by allowing leukocytic activity to resume function.

Mechanical Effect of Increased Pressure: Any gas in the body will decrease in volume as the pressure on it increases. With a threefold increase in pressure, a bubble trapped in the body is reduced by two-thirds. Thus, reduction in gas volume resolves air embolism and decompression illness when the diagnosis to treatment is done in a timely manner.

Vasoconstriction: High pressure oxygen causes constriction of the blood vessels in normal tissues without creating hypoxia. It does not cause constriction in previously oxygen-deprived tissues. The vasoconstriction decreases edema which is helpful in the treatment of burns, crush injuries, compartment syndromes, and other acute traumatic ischemias. Even though the blood flow that contributes to edema is reduced, oxygen delivery to the tissues is maintained through the hyperoxygenation effect.

Antimicrobial Activity: HBO2 inhibits alpha toxin production as seen in anaerobic infections such as clostridium perfringens (gas gangrene). The most common cause of gas gangrene is clostridium perfringens; however, there are several gas producing organisms (aerobic and anaerobic) that require surgical debridement initially. It also enhances the white cell killing activity which provides an excellent adjuvant to I.V. antibiotic and local wound care.

Mass Action of Gases: The flooding of the body with any one gas tends to "wash out" others. This action occurs more rapidly under pressure than under ordinary conditions, and makes HBO2 an indicated treatment for decompression sickness.

Reduction of Reperfusion Injury: Following an ischemic interval, indirect injury occurs which is mediated by the inappropriate activation of leukocytes. HBO2 prevents such activation. Adherence of white blood cells to capillary walls is markedly reduced, thus mitigating the "no reflow" phenomenon. This is why HBO2 therapy is indicated in carbon monoxide poisoning and is considered the treatment of choice.


What are the clinically accepted indications for Hyperbaric Oxygen Therapy?

According to the Committee Report by the Undersea and Hyperbaric Medicine Society, Inc., Revision 1996, the following conditions have been accepted for the primary or adjunctive use of hyperbaric oxygen.

Treatment of Choice:

Carbon Monoxide poisoning and smoke inhalation*

Decompression sickness*

Acute air or gas embolism*

Adjunctive Therapy:

Enhancement of healing in selected problem wounds

Preparation and preservation of skin grafts or flaps in compromised tissue

Crush Injury, compartment syndrome, and other acute traumatic ischemias*

Radiation necrosis: osteoradionecrosis and soft tissue radiation necrosis

Thermal burns

Chronic refractory osteomyelitis

Necrotizing soft tissue infections

Gas gangrene( clostridial myonecrosis)*

Certain case of exceptional blood loss anemia

*These conditions require immediate consultation for optimal results.


Is HBO2 therapy reimbursed by insurance?

If therapy is performed within the accepted indications published by the Undersea & Hyperbaric Medicine Society and as viewed by the Health Care Financing Administration, therapy is normally reimbursed.

Like all medical services provided, some private and all managed care providers require pre-authorization.


How is a hyperbaric treatment administered?

By definition, hyperbaric oxygen therapy is administered to a patient in a pressurized chamber. 

Monoplace Chambers: A monoplace chamber is a system that accommodates one patient at a time. The patient lies down on a stretcher which slides into the chamber. Typically the chamber is pressurized with 100% oxygen. The patient receives 100% oxygen by breathing the oxygen inside of the chamber. A mask or a hood is not needed as with a multiplace system. Monoplace chambers have the capability to go to 3 ATA of pressure. Other than decompression sickness and gas embolism, the UHMS protocols for hyperbaric therapy do not require greater than  3 ATA of pressure for treatment.   Critically ill patients requiring extensive life support equipment can be treated in the Sechrist monoplace. (Other monoplace manufacturers do not offer all the life support capabilities).

Advantages: Requires much less space than a multiplace chamber. Patient does not need to use a mask or a hood in order to breathe the 100% oxygen (important when dealing with head or neck injuries).


How long is a hyperbaric treatment?

Except for decompression sickness and arterial gas embolism, typical treatments are approximately  1.5 hours long. During routine therapy, patients can watch television, listen to the radio, or converse with the staff to help pass the time. Treatments are administered once on an in-patient or out-patient basis. In some acute cases, treatments may be administered every eight to twelve hours.


How many treatments are needed?

A patient's clinical response and other factors often dictate the number of treatments required. Emergency cases, such as carbon monoxide poisoning, arterial gas embolism or decompression sickness, may only require one or two treatments. Non-healing wounds may call for as many as 20 to 30 treatments.


What does a hyperbaric treatment feel like?

Depending on the type of chamber, a patient sits or lies comfortably during a treatment. Generally, the patient will feel no differently than if he or she were not in the chamber. However, during certain parts of the treatment, the patient may experience a sensation of fullness in the ears, similar to the feeling experienced on an airplane. This is a result of the eardrum responding to pressures changes. Prior to treatment, the patient will be taught a few easy methods to "clear" his or her ears to avoid discomfort.

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            Hyperbaric Oxygen Therapy   improves the defenses and responsiveness of a compromised host.  It may be used as an adjunct  to surgical debridement; resection of non-viable soft tissues or bone; antibiotic therapy, soft tissue flap reconstruction; and bone grafting as may be indicated. The increase in tissue oxygen tension in hypoxic bone and soft tissue has been shown to stimulate growth of functioning capillaries (angiogenesis), fibroblastic proliferation and collagen synthesis. This process reduces the extent of tissue death (ischemic necrosis) in impaired or jeopardized soft tissues or bone. An increase in success rates of bone and skin grafts to previously irradiated tissues in both animal models and human studies has been observed.

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GAS  LAWS

Boyle's Law:   P' V' = P" V"       Doubling the pressure decreases the volume by half.  

Henry's Law:   The amount of a gas dissolved in a liquid (in which it is in contact with and with which it does not combine) is directly related to the partial pressure of this gas.

Charles' Law:   V' / T'  =   V" / T"

Universal Gas Law:   P V = n R T

Dalton's Law:   total P = P' + P" + P''' + ...

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MECHANISMS  of  HYPERBARIC   OXYGEN  THERAPY

Effects of high oxygen pressures:   10 - fold increase in physically dissolved oxygen in tissues;   3 - fold increase in diffusion distance of oxygen into tissues;   effects lasting for 2 - 4 hours duration after treatment; vasoconstriction; enhancement of fibroblast proliferation and secretion; growth of new blood vessels; enhanced killing activity of WBC (white blood cells);  enhanced bone resorption / osteoclastic function; inhibition and killing of anaerobic bacteria; cessation of toxin formation (e.g. clostridia);  toxin inactivation (e.g. clostridia, Brown recluse spider); antibiotic synergism (e.g. aminoglycoside and amphotericin); improved transport of substances(e.g. antibiotics) across the blood-brain-barrier; flexibility of rbc membrane (red blood cells).

Usefulness in the Treatment of:   hypoxic conditions like toxic inhalation;  problems involving inadequate perfusion / circulation;  anemia, (vascular) states of shock; edema.  Please refer Main Page, section on "Indications"  and  "Investigational".

Solubility Coefficient of Oxygen:   0.022   ml O2  in  1 ml of blood @ 38'C, 760 mmHg pressure.                 1 ATA = 2 vol%           2 ATA = 4 vol%             3 ATA = 6 vol%

Note:   Oxygen tensions of  30  Torr in tissues are required for function and repair (versus viability)

By definition, HBO must be  1.4  ATA   or   greater.  Pressures below this are defined as          " topical" hyperoxia.

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Dr. Llorente / Florida Keys

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see links   for support group information

http://www.ehyperbaric.com

http://www.llorente.com/hyperbaric

http://209.130.115.193

http://www.netnet.net/mums/mum_whatis.htm

UHMS (Undersea and Hyperbaric Medical Society)

Tel. (714) 8 8 5 - 8 9 8 0